1. Field of the Invention
The present invention relates to a dispersion compensation unit which compensates for both the chromatic dispersion and dispersion slope of an optical fiber transmission line and an optical communication system including the optical fiber transmission line and dispersion compensation unit.
2. Related Background Art
To increase the speed and capacity of optical communication in an optical communication system for executing WDM (Wavelength Division Multiplexing) optical transmission, it is important to make the absolute value of accumulated chromatic dispersion in the optical transmission line in a wide signal wavelength band as small as possible. It is generally difficult in an optical transmission line using only a kind of optical fiber. Hence, the absolute value of accumulated chromatic dispersion in an optical transmission line in a wide band is reduced due to an optical transmission line formed by connecting a plurality of kinds of optical fibers.
For example, a dispersion compensation optical fiber disclosed in Japanese Patent Laid-Open No. 2001-337245 aims at compensating for both the chromatic dispersion and dispersion slope of a standard single-mode optical fiber having a zero dispersion wavelength near 1.3 μm and a positive chromatic dispersion (about 17 ps/nm/km) at 1.55 μm. The chromatic dispersion is −40 to −10 ps/nm/km at a wavelength in use within a wavelength band of 1.53 to 1.62 μm. In an optical transmission line formed by connecting the single-mode optical fiber and dispersion compensation optical fiber, when the length ratio of these fibers is appropriately set, the absolute value of the entire chromatic dispersion becomes small. In addition, the absolute value of the entire dispersion slope also becomes small.